What’s the Best Temperature To Work Out In? An Exercise Scientist Has the Answer

Recently, an editor at Well+Good received a hot tip from a celebrity trainer that exercising in cooler temps (specifically, a room with the AC cranking) could help improve your workouts by preventing you from overheating. The idea is that this helps you continue to perform at optimal levels for longer.

If this is true, however, then why are so many fitness brands offering heated classes for everything from Pilates (a favorite of Selena Gomez) to yoga to HIIT these days? What is actually the best temp to work out in?

The answer, according to Brittany Masteller, PhD, a research scientist for Orangetheory Fitness, is surprisingly similar to the ideal range for getting a good night’s sleep. “It’s safest to perform high-intensity workouts in a temperature-controlled space of approximately 68 to 72 degrees Farenheit,” says Dr. Masteller. (Approximately 68°F is the chef’s kiss for sleep, according to experts.) This is particularly true for certain populations like pregnant women and people with respiratory conditions like asthma, she says.

Of course, however, there are exceptions to every rule, including this one.

How temperature affects your workout performance

At its essence, exercise is a stressor on the body, and different workouts are designed to stress your body in different ways in order to get it to adapt. For example, when you lift heavy weights, you’re taxing your fast-twitch muscle fibers, which in turn helps them to get stronger. Or, when you perform vigorous aerobic exercise, like sprinting or HIIT, you’re causing your heart, lungs, and circulatory system (aka the cardiorespiratory system) to work harder, which increases your peak oxygen intake or Vo2 max. Both of these are beneficial to your overall health.

Similarly, tweaking the temperature of your workout above or below 68 to 72 degrees Farenheit can cause your body to adapt in positive ways, as long as you are properly hydrated, fueled, and fit to do so according to your doctor. The primary benefit to both hot and cold workouts is that they increase the cardio factor for the exercise that you’re doing because they force your brain and heart to work harder to keep your body in homeostasis. “The human body has ways of doing this, such as sweating when hot, or shivering when cold,” Dr. Masteller says.

“Fitness classes that are mostly low impact don’t tend to elevate the heart rate as much due to the nature of the workout,” she continues, “so adding heat to a lower-intensity workout adds another level of difficulty without changing the exercise prescription.” This tacks on a heart-healthy element to a workout that might otherwise not be considered aerobic.

FYI: It takes the average person 10 to 14 days to acclimate to working out in hot and humid conditions. But once you do, it comes with a few perks: “In people who are acclimated to exercising in hot and humid conditions, research shows improved heat transfer from the body’s core to the environment, improved cardiovascular function, more effective sweating, and improved exercise performance and heat tolerance,” Dr. Masteller says.

On the flip side, like in the heat, exercising in the cold makes your heart work harder to pump blood, which elevates your heart rate and can lead to improved cardiorespiratory fitness over time—even if you’re just going for a hot (cool?) girl walk in winter. Just be sure to dress appropriately, Dr. Masteller says, to keep warm without overheating because there is nothing cool about hypothermia.